7.7 Electrical Wiring (EWIS) Flashcards
What is the purpose of a continuity tester?
To verify that electrical connections are configured in accordance with the wiring diagram.
Continuity testing is essential for ensuring that circuits are correctly connected and operational.
What does insulation resistance testing help identify?
Current leakage and faulty or damaged insulation.
This testing is crucial to prevent arc faults, blown circuits, and risks of electrical shock or fire.
What is the main function of a bonding tester?
To ensure all components have the same potential to ground and prevent parallel paths for current flow.
Bonding is vital for safety and reducing electrical interference.
List the normal steps included in wiring checks.
- Visual inspection
- Continuity testing
- Insulation resistance testing
- Bonding testing
These checks are essential for troubleshooting and ensuring system integrity.
What should be done after completing all tests on wiring?
Inspect installations to ensure connections are secured and test equipment is removed.
Function checks of the services concerned should also be made.
What is the definition of continuity in electrical terms?
The condition of being unbroken or uninterrupted.
Continuity testing confirms electrical links within circuits.
What equipment is typically used for continuity testing?
A multi-meter set to the ohms range.
A simple lamp and battery can be used but are less effective in detecting small stray resistances.
True or False: It is safe to apply power to a circuit while using continuity test equipment.
False.
Applying power can damage the equipment and injure personnel.
What does a high resistance reading indicate in insulation testing?
There is little current flowing, indicating satisfactory insulation condition.
Low resistance indicates high current flow and potential insulation failure.
What is the typical voltage used in insulation testing for a 28 V system?
100 V.
This is a rule of thumb where testing voltage should be at least three times the normal working voltage.
What are the three main types of bonding?
- Equipment bonding
- Metallic surface bonding
- Static bonding
Each type serves different purposes for safety and functionality.
What is the role of grounding in electrical systems?
To provide a means for continuously discharging a charged conductive body to the earth.
Grounding is essential for safety and preventing electric shocks.
Fill in the blank: Insulation testing is typically carried out after _______.
[visual checks, bonding, and continuity tests].
This sequence ensures thorough verification of electrical systems.
What is the consequence of a bad crimp in wiring?
Increased resistance or infinity/open-circuit conditions.
Corrosion or contamination can also lead to similar issues.
What does good bonding help prevent?
- Radio interference
- Induced noise
- Localized hot spots
These issues can arise from high resistance earth return paths.
What must be done to ensure accurate insulation resistance testing?
Both ends of the cable, connector, or loom must be disconnected and isolated.
This protects systems from high voltages and internal damage.
What is the minimum resistance value allowed for single wires in insulation testing?
5 megohms.
For multiwire looms or wire-bundles, the minimum value is 2 megohms.
What is static bonding in aircraft?
Static bonding refers to the requirement for isolated conducting parts to have a secure electrical connection to the aircraft structure for static charge dissipation.
This ensures that static charges are safely discharged to prevent hazards.
What is the maximum resistance for bonding larger objects?
Less than 1 ohm when clean and dry.
Higher resistances are permissible for smaller objects.
What should be inspected during bonding inspection?
Inspect for:
* Arcing
* Conduit bond
* Corrosion
* Freedom of movement
Each of these factors is crucial for ensuring safe electrical bonding.
What can cause electrical arcing in bonding?
Intermittent electrical contact between conducting surfaces.
Arcing can be prevented by proper bonding or insulation.
How must metallic conduits be bonded?
Bonded to the aircraft structure at each terminating and breakpoint.
The bonding strap must be located ahead of the connected equipment.
What is the maximum resistance for exposed conducting frames?
Less than 2.5 mΩ to the structure.
A ground wire connection to terminals can satisfy this requirement.
What are the classes of aircraft electrical bonds?
Classes of electrical bonds include:
* Class A: Antenna installation (resistance < 2.5 mΩ)
* Class C: Current path return
* Class H: Shock hazard (resistance < 100 mΩ)
* Class L: Lightning protection (resistance < 0.05 Ω)
* Class R: RF potential (resistance < 2.5 mΩ)
* Class S: Static discharge (resistance < 1.0 Ω)
Each class serves a specific purpose in ensuring safety and functionality.
What is the purpose of a bonding tester?
To measure low resistance and assess the bonding or earthing systems on aircraft.
It functions as a sensitive analogue Ohmmeter.
What method does a bonding tester use to measure resistance?
The four wire method, or Kelvin method.
This method allows for accurate measurements independent of test lead resistance.
What is required before starting a bonding test?
Check the battery state and obtain full-scale deflection with shorted probes.
Ensure the meter reads zero when shorting with the long cable probe.
What must be done to the protected points before testing?
Remove or pierce protective treatments like paints and coatings.
This ensures direct contact for accurate resistance measurement.
What is an earth point?
A location where electrical earth and neutral terminations are made.
Earth points are crucial for AC and DC systems’ return paths.
Why must AC neutral wires and DC earth wires not be connected to the same earth post?
To prevent feeds from the AC neutral through the DC system to earth.
This protects the integrity of the electrical systems.
What must be tested when earth posts or terminal blocks are fitted or replaced?
They must be electrically bonded to the aircraft structure.
This involves a bonding test followed by a millivolt drop test.
What is the maximum resistance for bonding between components and the main earth?
Must not exceed 0.05 Ω.
This ensures effective grounding and bonding.
What is the purpose of a corrosion tag in earth post assemblies?
To prevent electrolytic action between the assembly base and the airframe structure.
This helps maintain electrical integrity.
What is the significance of flexible fuel pipes being bonded internally?
They create a leak-proof joint at the end connections for good electrical bonding.
The resistance must not exceed specific values for reliability.
What is a digital bonding tester used for?
To measure bonding resistance in a digital format.
This provides a more modern and potentially easier method of testing.
What is wire stripping?
A critical primary process associated with crimping that removes insulation from wires.
What are the types of wire stripping tools commonly used?
- Single Blade or Scalpel
- Double Blade
- Thermal
Which wire stripping tool is the preferred option?
Double Blade
What is the purpose of crimping tools?
To apply pressure across a wire/contact connection, securing the conductor to a termination.
What is the crimping process?
- Selection of strip tool
- Stripping the wire
- Inspecting the strip
- Inserting the contact
- Crimping the new contact
- Testing the connection
What are the common types of hand crimping tools?
- M22520 series crimp tools
- AMP PIDG Crimp Tool
- AD1377 In-Line Sealed Splice Crimp Tool
Describe the operation of crimping tools.
They apply pressure to crimp a wire into a contact, ensuring a strong joint through cold flow of metal.
What is a Go/No-Go gauge?
A tool used to check the calibration of crimping jaws by ensuring proper crimp tolerance.
What do the M22520 series crimp tools accommodate?
Contacts with wire barrel sizes from 12 to 28 and wire sizes from 12 to 32.
What is the consequence of using incorrect stripping tools?
- Reduction in current-carrying capacity
- Reduction in insulation protection
- Unacceptable mechanical or electrical characteristics
Fill in the blank: A crimped connection is one in which a cable conductor is secured by _______ to a termination.
[compression]
True or False: Hydraulic crimping machines are typically used on the aircraft.
False
What inspection should be carried out before using crimping tools?
- Checking for bruised or nicked conductor strands
- Inspecting for kinks in the wire
- Ensuring no jagged cuts to insulation
What is the purpose of the self-locking ratchet in crimping tools?
To prevent the tool from opening until the crimp sequence is complete.
List the stages of the hand-strip tool operation.
- Relaxed
- Half Pressure
- Full Pressure
- Half Released
- Fully Released
What are the two types of hydraulic crimping tools mentioned?
- Hand-held crimping tools
- Hydraulic crimping machines
What happens if the ‘GO’ gauge does not pass through the crimp tool?
The tool should not be used and must be returned for repair.
What is the function of the turret head in crimping tools?
To position the contact correctly for crimping.
What is the significance of strip length in crimping?
It is critical for ensuring the strength of the crimp and termination.
What types of crimping tools are designed for hydraulic operation?
- Hydraulic Hand Crimp Tool
- Electric/Hydraulic Crimping Machine
What is the main advantage of hand-held hydraulic crimp tools?
They are portable and allow for work on aircraft at the point of crimp.
What must be done after crimping a new contact?
Inspect the new crimp, contact, and wire.
What is the purpose of the ‘GO’ and ‘NO-GO’ gauges in crimp tool testing?
‘GO’ gauge passes through the tool jaws; ‘NO-GO’ gauge does not pass through
If ‘GO’ gauge does not pass or ‘NO-GO’ gauge passes, the tool is unserviceable.
What should be done if a crimp tool is found to be unserviceable during testing?
Withdraw the tool from service
The tool must be returned for repair.
What is the first step in carrying out a gauge test on a crimp tool?
Set wire selector to the appropriate position based on the tool being tested
Position No. 4 for M22520/1-01 or No. 8 for M22520/2-01.
True or False: The ‘NO-GO’ gauge must enter the closed jaws of a serviceable crimp tool.
False
The ‘NO-GO’ gauge must not enter the closed jaws.
What are the key aspects tested for crimp tools at calibration workshops?
Resistance, millivolt drop, and tensile strength
These tests are against a laid down standard.
What must be checked before using any crimping tool?
The calibration tag must be checked for validity
If the tag is out of date, the tool must not be used.
What are the characteristics of contacts in relation to wire gauge sizes?
Contacts are assigned to a family of connectors based on current-carrying capability
Diameter sizes follow the American Wire Gauge (AWG) standard.
Define ‘crimping’ in the context of wire terminations.
Crimping is a process where distortion of the terminal shank secures it to the conductor
It results in a cold flow of metal for good electrical and mechanical properties.
What is the ideal shape of a crimp, and what shape is commonly found in practice?
Ideally round, but hexagonal shapes are commonly found
Hexagonal shapes yield excellent results and are applicable to various cable sizes.
What type of terminal lugs are commonly used in aviation, as manufactured by AMP?
Pre-Insulated Diamond Grip (PIDG) terminal lugs
They are designed to be vibration resistant and provide good electrical conductivity.
What are the four important design features of the AMP crimping tool?
- Certi-crimp ratchet
- Locator
- Insulation adjusting pins
- Colour and dot coding
These features ensure constant quality of the crimp joint.
What does the Certi-crimp ratchet ensure during the crimping process?
It ensures the bottoming of the die jaws before they can be opened again
This prevents under crimping.
What is the function of the locator in the AMP crimping tool?
It clamps the terminal in the correct position and allows conductor strands to protrude correctly
It ensures proper insertion of the conductor into the terminal.
Fill in the blank: The insulation adjustment pins allow for variation in insulation diameter and wear in the tool. The three degrees of adjustment are ______, ______, and ______.
Loose, Medium, Tight
What does the ‘dot’ coding system in AMP tools indicate?
It identifies terminals crimped in the correct AMP hand tool and their correct positioning
Different dot codes correspond to different tool sizes.
What should be done if the test date for a crimping tool has expired?
The tool must not be used and should be considered unserviceable
It must be returned for a check.
What is the role of insulation adjustment pins during crimping?
To ensure proper insulation grip during the crimping process
They must be set to the same position number for both pins.
Describe the crimping procedure for AMP terminal lugs.
- Strip wire to specified length
- Insert terminal into jaws
- Insert wire into terminal
- Crimp until ratchet releases
- Inspect crimp
Follow SWPM or ESPM for detailed dimensions.
What is a dual crimp in the context of in-line splices?
A splice that requires crimping both ends of the splice to the wire
The cable and splice must enter the tool correctly.
What is the function of the insulation crimp adjustment indicator on the AMP 59250/59275 crimping tool?
To control the crimp height of the insulation barrel
It can be set at any of four positions corresponding to insulation diameter.
What does the inspection procedure for crimping tools involve?
Check for calibration, visually inspect for missing parts, and note the return action of handles
Inspect die closure surfaces for damage as well.
What is the significance of the pre-set crimp depth in environmental sealed splices?
It provides optimal tensile strength and insulation integrity
The ratcheted release ensures full closure to prevent under-crimp.
What does it mean for a tool to be considered unserviceable (U/S)?
If any parts are missing or the tool is defective
What is the function of the AD1377 crimp tool?
Designed for environmental sealed splices with a pre-set crimp depth for optimum tensile strength and insulation integrity
What is the purpose of the ratcheted release in the AD1377 crimp tool?
Ensures full closure of the tool to help prevent under-crimping
What steps should be followed to assemble an In-Line Sealed Splice?
- Select the correct splice set
- Strip the insulation to the required length
What should be observed when positioning the wire in the butt splice?
- Conductor visible in inspection hole
- Conductor does not overlap wire stop
- Insulation not in crimp barrel
- Wire insulation maximum 0.13 in from crimp barrel end
What is the first step after crimping the splice?
Repeat the steps prior to assembling the other end of the butt splice
What should be done after completing the splice?
Use a heat gun to shrink the sleeve into position
What is the function of the M22520/5-01 and M22520/10-01 crimp tools?
Utilize sets of interchangeable dies for different AWG and cable crimp formats
What is the wire size range for which M22520/5 and M22520/10 crimp tools are approved?
Sizes 26 through 10 splices and terminal lugs
What is the purpose of the positive ratchet assembly in the crimping tools?
Controls complete handle movement in both directions
What types of crimp dies are available for the M22520 crimp tools?
Hexagonal crimp dies with single, double, and triple cavity designs
What must be done before using the crimping tools?
Check tool for periodic calibration and proper adjustment
Fill in the blank: The terminal lug should be inserted _______ first into the wire side of the hand tool barrel crimping jaws.
tongue
What should you do after inserting the stripped wire into the terminal lug barrel?
Squeeze tool handles until the ratchet releases
True or False: The crimping dies can be permanently secured by driving a rolling pin into the holes provided.
True
What types of connectors do the crimping dies accommodate?
Most co-axial and bi-axial connectors and contacts
What is the first step in the crimping procedure for pre-insulated copper terminal lugs?
Strip wire insulation as per SWPM or ESPM procedures
What should be examined after removing the completed assembly from the crimping tool?
Examine it for proper crimp
What is Hydraulic Hand Crimping Tool PN 59974-1 designed for?
Crimping terminals and splices for wire size from AWG 2 to 8
Example usage includes main generator cables
What are the two levers on the Hydraulic Hand Crimping Tool used for?
A stationary lever and a movable lever to pump hydraulic fluid behind the ram
What is the function of the crimping die in the Hydraulic Hand Crimping Tool?
To close around the terminal and splice, securing them during crimping
What part number is associated with the crimping die for the Hydraulic Hand Crimping Tool?
48755-1
What is the first step in die insertion for the Hydraulic Hand Crimping Tool?
Pull out the latch pin and open the yoke
What must be done before inserting dies into the head of the Hydraulic Hand Crimping Tool?
Loosen the socket head cap screws holding the insulation crimping section of dies
How many insulation crimp positions do the dies have?
Three positions: loose, medium, and tight
Fill in the blank: The insulation crimping section of the die is in the ______ position when the pin key is pushed all the way in.
loose
What should be done if the insulation crimp does not grip or support wire insulation as required?
Loosen the socket head cap screws and set the pin keys to the medium position
What is the correct terminal positioning for crimping in the Hydraulic Hand Crimping Tool?
The bottom of the terminal tongue must face the stationary die
True or False: The movable lever must be pumped until the dies have bottomed for a complete crimp.
True
What must be done after crimping to release the pressure in the Hydraulic Hand Crimping Tool?
Turn the movable handle to actuate the striker
What is the purpose of the visual inspection after using the crimping tool?
To verify that all retaining pins are in place and inspect for damage
What are typical signs of die damage that should be visually inspected?
Flattened, broken, pitted, or chipped conditions
What is the function of the AMP 69120 Series Electric/Hydraulic Crimping Machine?
Provides a portable hydraulic power source for crimping large wire sizes
What voltage options are available for the AMP 69120 Electric/Hydraulic Crimping Machine?
115 VAC and 220 VAC
What does the multi-directional valve in the hydraulic crimping setup allow?
Operation of more than one crimping head from the pump
What is the first step when using the handle control for the crimping machine?
Attach the hose assembly
What should be done if the ‘RUN’ switch is depressed too long during crimping?
The dies will close fully and crush the terminal or splice
How should the wires be oriented when crimping with rectangular conductors?
So that the crimping pressure is applied to the flat side of the conductors
What is the primary function of the Hydraulic Crimp Head 1752787-1?
Accepts interchangeable die sets for heavy-duty terminals and splices
What is required for die insertion in the Hydraulic Crimp Head?
Ensure the matched die set, terminal, and wire size are correct
What must be done to secure the moving die in the Hydraulic Crimp Head?
Tighten the setscrew after inserting the moving die
What is the process of testing crimp joints?
The process includes:
* Visual Inspection
* Tensile Test or ‘Pull Test’
* Volt Drop Test
Define tensile strength in relation to crimp joints.
Tensile strength refers to the maximum load a crimp joint can withstand without breaking, ideally close to the tensile strength of the wire or cable.
What does the volt-drop test measure in crimp joints?
It measures the voltage drop across the crimp joint, indicating the resistance created by the joint.
What is the purpose of the crimp joint test?
To ensure the mechanical strength and electrical conductivity of the crimped joint, confirming its airworthiness.
What is the first step in ensuring the quality of a crimp?
A visual inspection to verify the correct crimp procedure has been followed.
What is the consequence of over-crimping a crimp termination?
It reduces the circular area of the conductor, increasing electrical resistance.
What does a simple ‘Pull Test’ ensure?
It ensures the integrity of the crimp joint and that the contact is properly seated.
What are the general rules for inspecting crimp joints?
General rules include:
* Proper tooling and parts used
* Conductors completely in the crimp barrel
* Insulator outside
* No damage to conductor or insulator.
What is the typical range of tensile strength for crimp joints?
The tensile strength must be close to the tensile strength of the wire or cable.
What is the significance of the resistance of the joint?
The resistance of the joint must be negligible compared to the resistance of the wire.
What is the formula related to volt-drop testing?
The formula is V=IR, where V is voltage, I is current, and R is resistance.
What is the role of calibration in crimping tools?
Calibration ensures that the crimping tool meets specific manufacturer requirements for effective crimping.
True or False: A full tensile strength and millivolt drop test must be carried out after every crimp.
False.
What is the typical method for testing tensile strength?
The ‘Pull and Break’ or ‘Pull-Apart’ load method, applying increasing axial force until separation or breakage occurs.
What should be verified during the visual inspection of crimp joints?
Verification includes crimp indentations, insulation removal length, and absence of defects.
Fill in the blank: The insulation must be between _______ from the end of the contact.
1/64 in to 1/32 in (0.4 mm to 0.79 mm)
What must be ensured regarding PIDG terminal lugs during inspection?
Crimp indent is centered on the terminal lug barrel and conductor extends beyond the barrel by approximately 0.8 mm.
What happens if a defective connection is found during visual inspection?
The defective connection must be cut off and remade using a new terminal lug.
What are the two types of contacts used in aircraft connectors?
Front release and rear release
Contacts are referred to as pins (male) and sockets (female)
Define front release contacts.
Contacts removed from the front of the connector using an extracting tool
The tool fits around the contact and pushes it out the back
Define rear release contacts.
Contacts removed from the back of the connector using a contact removal tool
The tool releases the contact retention clip
What is the purpose of environmental seals in connectors?
To preserve the seal when no contacts are fitted
Achieved using fillers or blanking fillers
What is the role of contacts in electric connectors?
To connect individual wires in a circuit
Pins fit inside sockets to form electrical connections
What is the significance of the ‘engaging end’ of a contact?
It fits into the holes of the connector and is standardized by AWG size
The other end is referred to as the ‘crimp barre’
What color tool is used for AWG 12 contacts?
Yellow tool
What color tool is used for AWG 16 contacts?
Blue tool
What color tool is used for AWG 20 contacts?
Red tool
Describe the removal procedure for front release contacts.
Align the tool, push into the insert hole, release springs, and advance the slider to eject the contact
Care must be taken to avoid bending contacts
What is a common identification feature of rear release connectors?
A blue band around the shell or a blue line on the back shell
True or False: The rear release connector is easier to identify contact positions due to visible wires.
False
What is the procedure for inserting rear release contacts?
Press wire into the colored slot, hold connector, insert contact, listen for a metallic click
Ensure contacts are inserted in the correct order
What must be done after installing each contact?
Test for satisfactory retention
What tool is used to remove unwired contacts?
Unwired contact removal tool
Describe the procedure for removing contacts from terminal blocks.
Use approved extraction tool, snap white end over wire, slide into cavity, and pull out wire and tool simultaneously
Fill in the blank: Pins are ______ contacts.
male
Fill in the blank: Sockets are ______ contacts.
female
What are the components of a front release removal tool?
Handle, tip, plunger (sometimes spring-loaded)
What indicates that a contact is seated correctly in a module?
A clicking sound followed by increased resistance
What are the losses associated with co-axial cable?
Transmission line losses:
* Copper losses
* Dielectric losses
* Radiation losses
* Induction losses
Each type of loss affects signal integrity and overall performance.
What is the importance of characteristic impedance in co-axial cables?
Characteristic impedance must be matched to the circuit to prevent reflected waves that can damage the transmitter
Mismatched impedance can lead to signal degradation and increased losses.
What does VSWR stand for?
Voltage Standing Wave Ratio
It measures the efficiency of power transmission in a cable.
What effects can badly crimped or corroded connectors have?
They can cause reflected waves, damage the system, and create localized cable hot spots
This can significantly impact the performance of RF systems.
What tool is used for the assembly and crimping of co-axial cables?
DMC HX4 tool
This tool facilitates proper crimping techniques necessary for reliable connections.
What are the handling precautions for co-axial cables?
Never:
* Step on the cable
* Place anything heavy on it
* Bend it sharply
* Use it as a handle
* Pull it except in a straight line
Careful handling is vital to maintain the integrity of the cable.
What materials are commonly used as dielectric in flexible co-axial cables?
Foam or polyethylene
These materials are chosen for their resistance to various fluids and for weight-saving properties.
What are copper losses in co-axial cables?
Power loss (I²R) due to resistance in the copper conductor and losses due to the skin effect
The skin effect causes AC currents to flow near the surface of the conductor.
How can dielectric losses be reduced?
By selecting materials with atomic structures that are easily distorted, such as foam nylon or polyethylene
These materials minimize heating of the dielectric insulation.
What causes radiation losses in co-axial cables?
Escape of electromagnetic energy due to imperfections in insulation or discontinuities in the outer conductor
Radiation losses can lead to signal interference.
What are induction losses in coaxial cables?
Energy loss caused by eddy currents induced in the outer conductor due to the magnetic field created by current in the inner conductor
This can lead to signal distortion, particularly at higher frequencies.
What are the consequences of poor termination in co-axial cables?
Increased losses, reflected waves, and potential system damage
Proper termination is critical to maintain signal integrity.
What are the common installation precautions for co-axial cables?
Avoid clamping too tightly, sharp bends, and ensure proper support at intervals of 61 cm (24 in)
These precautions are necessary to prevent internal damage that may not be visible externally.
What is the minimum bend radius for co-axial cables?
Six times the diameter of the cable
This prevents kinking and maintains electrical performance.
What types of connectors are commonly used with co-axial cables?
Bayonet Nut Coupling (BNC) and Threaded Nut Coupling (TNC)
These connectors are designed for secure and reliable connections.
What is the purpose of the K-Grip sleeve in co-axial connectors?
It provides a grip and secures the connector to the cable’s outer insulation
Proper assembly is crucial for maintaining connection integrity.
What is the function of the crimping tool M22520/5-01?
It is used for crimping co-axial connectors
This tool features interchangeable dies for different applications.
What are the five main stages of co-axial cable preparation?
- Removal of the outer jacket
- Braid cut to the correct length
- Dielectric cut to the correct length
- Inner conductor cut to the correct length
- Stripping according to dimensions
Proper preparation is essential for a quality co-axial connection.
What is the first step in preparing a co-axial cable for crimping?
Slide the Ferrule Over the Cable Before Stripping the Jacket, Dielectric and Braid
This step ensures that the ferrule is positioned correctly before any stripping occurs.
What should you verify before crimping the centre pin?
Verify centre pin position prior to crimping
Ensuring the correct position of the centre pin is crucial for a proper connection.
What is the purpose of applying a secondary crimp?
Achieve a crimp over the full length of the ferrule
This ensures a secure and effective connection.
List the visual confirmations important in co-axial crimp examination.
- Correct form of the HEX crimp (not over-crimped or under crimped)
- No loose strands of braiding
- No exposed conductor strands
- No obvious damage or mis-shaping to the dielectric
- No obvious damage to the inner ferrule
- No obvious damage to the inner conductor pin
- The inner conductor pin is straight
- No obvious damage to the Threaded Portion (TNC)
- No obvious damage to the Bayonet (BNC)
- No obvious damage to the outer sheath
These confirmations ensure the integrity and reliability of the co-axial connection.
What are the procedures for testing co-axial cables upon installation?
- Continuity for each of the two conductors
- Insulation resistance checks
- Time Domain Reflectometer (TDR) testing
- Characteristic Impedance
- Open circuit conditions
- Short circuit conditions
These tests help ensure that the cable is functioning correctly and safely.
True or False: The Time Domain Reflectometer (TDR) is used to detect cable damage.
True
The TDR can identify alterations in the electrical properties of the cable.
How does the Time Domain Reflectometer (TDR) function?
It sends an electrical pulse onto the cable segment under test and displays the echo of the pulse
This allows for the characterization and location of faults.
What should be done before using the TDR?
- Familiarise yourself with the test set
- Read the operating manual and AMM procedure fully
- Set up the required pulse width for the system, cable, and requirement
These steps are crucial for accurate testing and safety.
Fill in the blank: If the cable is in good condition, the pulse energy is consistent throughout and dissipates at the _______.
end of the cable
This indicates an open cable on the readout.
What does a reflected pulse indicate when using the TDR?
Changes in the impedance
Reflections in the pulse waveform can indicate the presence of faults or discontinuities.
What must be determined from the aircraft manuals before using the TDR?
The original length of the co-axial cable
This is necessary for identifying the open end of the cable.
What is the primary purpose of properly selecting, installing, and maintaining electric wiring in an aircraft?
To ensure the safety of the aircraft.
List the factors that affect wire selection for aircraft wiring.
- Design temperature
- Flexibility requirements
- Abrasion resistance
- Strength
- Insulation
- Electrical resistance
- Weight
- Applied voltage
- Current flow
What is typically referred to as a ‘wire’ in aircraft terminology?
Any type of single conductor surrounded by insulation.
What materials are commonly used for coating aircraft wiring to prevent oxidation?
- Tin
- Silver
- Nickel
What is the primary disadvantage of using a cable in aircraft wiring?
The inability to repair or replace a single wire.
What are ‘Airframe’ cables designed for?
To satisfy the requirements of ‘Open’ airframe wiring and general wiring of power plants.
What is a key characteristic of ‘Interconnect’ cables?
They employ thinner insulation than airframe types.
What is the purpose of Equipment Cable?
Intended for use within equipment and is very flexible.
Fill in the blank: The most common type of thin-wall cable is _______.
Kapton
What is the difference between fire-resistant and fireproof cables?
Fire-resistant cables operate for five minutes in fire; fireproof cables operate for fifteen minutes.
What type of cable helps minimize interference with aircraft instrumentation?
Shielded Cable
True or False: Data bus cables can be replaced by any other type of cable.
False
What is the purpose of Power Feeder cables in an aircraft?
To provide high load outputs to the electrical distribution system.
What system is used for identifying wires and cables in modern aircraft?
ATA 100 specification.
What technique is used to imprint wire codes onto modern cables?
Hot stamping.
What does the letter ‘D’ signify in cable coding?
General instruments.
What is the maximum number of digits in a wire number?
Five digits.
What is the significance of the wire segment letter in wire coding?
It discriminates between wires sharing a common terminal.
Which letter is used to identify a ground wire in the wire identification code?
N
What is a common use for the suffix ‘AL’ in wire identification?
Indicates Alumel.
What does the wire gauge indicate in wire identification?
The American Wire Gauge (AWG) size of the wire or cable.
Why is it important to refer to the Wiring Diagram Manual (WDM) when identifying wires?
To determine which pieces of equipment a particular wire is connected to.
What is the primary characteristic of the Boeing Wire Identification System?
Information can be found in the ‘FRONT MATTER’ chapter of the Boeing Wiring Diagram Manual.
What does the applicable airworthiness code depend on?
The type of aircraft in which the cable is to be installed.
Which system forms the basis for the principles of the wire identification system?
ATA 100 system.
Where can information about the Boeing Wiring Numbering System be found?
In the ‘FRONT MATTER’ chapter of the Boeing Wiring Diagram Manual under ‘INTRODUCTION’.
What does the Boeing Wiring Diagram Manual (WDM) include?
Diagrams, drawings, and wire lists that define the wiring and hook-up of associated equipment.
What is the purpose of the wire list from Boeing?
It reflects all the wire bundles within an aircraft, listing bundle number, part number, description, and wires.
How is each wire bundle identified?
Each wire bundle is given an item number beginning with ‘W’.
What does the wire number in Boeing’s system consist of?
The wire identifier and the gauge.
What is the wire type code in Boeing’s wiring system?
A two-character identifier for the type of wire used.
What does the ‘Fam’ field in the wire number indicate?
The family of wires that are physically related, such as twisted or shielded wires.
How is the length of the wire indicated in the Boeing system?
In the FT-IN field, shown in feet and inches.
What is the significance of the diagram field in the Boeing wiring system?
It reflects the diagram on which the wire appears in the Wiring Diagram Manual.
What must be done with spare wires in Boeing’s system?
They can be used by the customer for kit and service bulletin incorporations.
How is wire identification done in Airbus systems?
By a ‘numerical plus a colour’ identification code.
What does the first 4 digits of an Airbus wire number represent?
The ATA system to which that wire belongs.
What is the main goal of wiring inspection criteria?
To minimize the risk of mechanical damage and damage by fluids or vapours.
What is the recommended routing for cables connected to apparatus?
Cables must run downwards from the apparatus wherever possible.
What must be ensured regarding cable support?
Cables must be supported at intervals of not more than 61 cm (24 in).
What is the warning associated with exposed or damaged live wires?
Risk of electrocution and electric fires.
What should be done before starting an inspection of an aircraft’s electrical system?
Turn off electrical power.
What is the minimum bend radius for a wire bundle?
Five times the outside diameter.
What must be done with unused wires in an aircraft?
They must be dead-ended, tied into a bundle, and secured to a permanent structure.
What should be done if wiring shows signs of overheating?
Check wiring to find the reason for increased temperatures.
What is the requirement for replacing wiring with defects?
Wiring must be replaced with equivalent wire.
What should not be used for primary support of wires and cables?
Tape, tie straps, or cord.
What is a cable loom?
A group of wires tied at regular intervals to form a semi-rigid assembly identified with a wire bundle number
It is specific to an aircraft system.
What is the purpose of wiring in a modern aircraft?
To provide primary power, analogue sensor signal voltage, system data, and feedback to aircraft systems
This includes distribution to Line Replaceable Units (LRUs), sensors, and computers.
What does ‘loom routing’ refer to?
The path the loom takes and the specified ‘run’ it follows between equipment or components within the aircraft.
What is the minimum bend radius for wire groups or bundles?
10 times the outside diameter of the largest wire or cable
At terminal strips, the radius can be three times the diameter.
What are the key requirements for cable loom support?
Prevent chafing, mechanical strain, arcing or overheating, interference, excessive movement, and facilitate re-assembly
Support wires through bulkheads and junction boxes.
True or False: Cable ties should be used in high vibration areas.
False
Plastic cable ties are not approved for use in high vibration areas.
What is the recommended spacing for ties in high vibration areas?
Maximum of 2 inches (5.08 cm) in engine and pylon areas, 6-8 inches (15.2-20.3 cm) in other high vibration areas.
Fill in the blank: Cables must be installed with sufficient _______ to prevent mechanical strain.
slack
What is the recommended method for providing adequate slack in wiring?
A loop in the wiring can be preferred for enabling equipment removal and replacement.
What are the general precautions when lacing or tying wire groups?
Lace or tie tightly enough to prevent slipping but not so tightly that it deforms insulation
Be careful with co-axial cables.
What materials can be used for making ties?
Waxed cotton cord, nylon cord, or fiberglass cord
Pressure-sensitive vinyl electrical tape is also permitted under certain conditions.
What is the purpose of self-clinching cable straps?
To tie and support cable assemblies and wire bundles quickly.
What should be checked during loom assembly?
Individual wires, including terminals, must be checked for continuity point to point following the wiring diagram.
What are the types of cable clamps mentioned?
P Clips, Loop clamps, and cable troughs
These are used to secure wire bundles.
What is the maximum distance from the terminal to the nearest point of cable support?
6 inches (measured along the cable).
What is the acceptable distance between clamps used to support wire bundles?
Do not exceed 24 inches (61 cm).
What is the effect of extreme temperature changes on aircraft cables?
They can suffer damage due to rapid temperature changes.
What is the correct way to form cable looms?
Using finger pressure only and without creasing the insulation.
What should be done at the ends of conduits carrying electric cables?
Prepared or bushed with insulating material at entry points to reduce damage risk.
What must be ensured for cables within conduits?
They must be capable of withstanding moisture encountered.
What is the significance of wire bundle breakouts?
They must curve smoothly from the bundle to prevent chafing and system failure.
What type of lacing should be used for wire bundles larger than 1 inch in diameter?
Double cord lacing.
What is the main consideration for aircraft cables?
Reliability, as it affects aircraft performance and safety.
What is the purpose of protective sleeving techniques?
To protect cables from damage due to heat and environmental factors.
What should be avoided when using cable ties on wire bundles that contain co-axial cables?
Do not use ties that can cut into or deform the insulation.
What is the primary function of clamps on wire bundles?
To hold the wire bundle secure and prevent abrasive movement
Clamps must not crush or pinch the wire.
What types of wires are allowed to cross each other under loop clamps?
Only multiple conductors twisted cables
Other wires and cables can be damaged.
What materials must clamps and support devices be compatible with?
Temperature, fluid resistance, UV light exposure, and mechanical loads
This ensures durability and safety in their installation environment.
What is the maximum spacing allowed between clamps?
24 inches (61 cm)
This spacing is critical for proper support.
What must be used to support wire bundles along the run?
Clamps lined with non-metallic material
Tying can be used between clamps but is not a substitute for adequate clamping.
What is the minimum clearance required between the bulkhead cut-out and the wire bundle?
3/8 inches (0.95 cm)
If this clearance is not met, a suitable grommet must be installed.
What should be done with wires at risk of chafing?
Use protective strapping
Spiral or ‘SPI.WRAP’ tape is a common method.
How much should ‘cable-droop’ be limited to when light pressure is applied?
0.5 inches (1.27 cm)
This helps maintain proper wire bundle integrity.
What is the recommended separation distance when routing wiring parallel to plumbing lines?
At least 6 inches (15.24 cm)
This helps prevent potential hazards.
What must be installed to protect wires located in wheel wells?
Sleeves of flexible tubing
These sleeves must be securely held at each end.
What is the maximum allowable bundle diameter in a conduit?
80% of the internal diameter of the conduit
This ensures proper fit and function.
What is heat shrink tubing used for?
To insulate wires and provide abrasion resistance
It also offers environmental protection for conductors.
What are the three main categories of heat shrink tubing?
- Thin-wall
- Medium-wall
- Thick-wall
Each category has different applications and properties.
What is the standard heat shrink ratio used in aircraft?
2:1
Higher ratios may be used for specific applications.
What precautions should be taken when using a heat gun?
Keep it away from flammable materials and ensure proper ventilation
Always follow safety guidelines to prevent burns or asphyxiation.
What is the purpose of self-fusing insulation tape?
To provide loom build-up and protection
It stretches as applied, allowing it to fuse to itself.
What is the recommended procedure for heat shrink application?
Select tubing, cut to length, apply heat, and ensure proper overlap
Protect adjacent wires from heat damage during the process.
What is the key reason for conducting cable inspections?
To maintain airworthiness and prevent system failures
Regular inspections are necessary due to environmental factors affecting wiring.
What material is commonly used for thin wall wire insulation in aircraft?
Aromatic polyimide insulation (Kapton®)
This material helps reduce weight while maintaining strength.
What should inspections focus on regarding the condition of aircraft wiring?
- Maintaining cleanliness
- Preventing dust and debris build-up
- Identifying defects
Inspections help ensure continued airworthiness.
What is the purpose of a maintenance plan for aircraft wiring?
To lay out the necessary inspections required for each aircraft type
This plan is developed due to the complexity of aircraft wiring systems.
What is typically done to wiring harnesses at a major check?
They are regularly deep cleaned
Cleaning may occur sooner if a requirement is deemed necessary.
What two types of inspections are carried out more frequently at lower check levels?
Visual Inspections (VI) and General Visual Inspections (GVI)
These inspections are part of routine maintenance.
List three items covered within the Installation/Inspections of aircraft wiring.
- Cable/Loom routing
- Cable/loom security
- Cable breakouts
Additional items include Cable Bend Radius, Cable and loom support and stand-offs, and more.
What factors determine the frequency of wiring checks?
The operation involved and the service schedule employed
Different operations may have different requirements for wiring checks.
Fill in the blank: A complete inspection of the wiring is conducted after a _______.
[major check]
This is part of the standard maintenance procedure.
True or False: Wiring of an aircraft is considered a system in its own right.
True
Advances in cable insulation materials have led to this development.
What does the cable bend radius refer to in aircraft wiring?
The minimum radius that a cable can be bent without damage
This is critical for maintaining cable integrity.
What are cable clamps used for in aircraft wiring?
To secure cables and prevent movement or damage
Proper clamping is essential for ensuring cable safety.
What should you be able to explain regarding EWIS by the end of the section?
You should be able to explain:
* EWIS inspections, maintenance, repair, and cleanliness tasks
* Typical EWIS degradation areas
* Examples of damages leading to EWIS repair
* Steps of the Enhanced Zonal Analysis Procedure (EZAP)
* Principal causes of wiring degradation
* Analysis of accidental contamination
* Application of preventive maintenance tasks
These points ensure comprehensive understanding of EWIS and its maintenance.
What does EWIS stand for?
Electrical Wiring Interconnect System
EWIS is crucial for the safe and economic operation of aircraft.
Why is reliability a main consideration for an aircraft wiring system?
The performance and safety of the aircraft, its crew, and its passengers depend on the correct functioning and integrity of an electrical circuit under all flight conditions.
What are Line Replaceable Units (LRUs)?
Modules and card files that house individual systems and computers in modern aircraft.
What are some typical uses and considerations for aircraft wiring?
Typical uses and considerations include:
* Power supplies (e.g., 28 V DC, 115 V AC)
* Analogue voltage outputs
* Sensor outputs
* Discrete ground inputs
* Formatted data exchange (e.g., Arinc 429)
* High-Intensity Radiated Fields (HIRF) protection
* RF energy inputs
* Size and miniature connections
* High-temperature areas
* Environmental considerations
* Fire-wire
These factors are essential for ensuring safe operations.
What can cause wire degradation in EWIS?
Principal causes of wiring degradation include:
* Inadequate maintenance
* Contamination
* Improper repair
* Mechanical damage
Age is not the sole cause of degradation.
What types of contaminants were found on wiring leading to accidents?
Contaminants included:
* Dust
* Dirt
* Metal shavings
* Lavatory wastewater
* Coffee
* Soft drinks
* Napkins
These contaminants can increase fire risks.
What does the Aging Transport Systems Rulemaking Advisory Committee (ATSRAC) focus on?
It focuses on establishing standard requirements for ensuring the integrity of aircraft wiring during design and production.
What are the three documents issued by EASA for EWIS maintenance?
The three documents are:
* AMC 20‐21: EWIS maintenance program
* AMC 20‐22: EWIS training program
* AMC 20‐23: Electrical Standard Wiring Practices documentation
These documents guide maintenance and reduce wiring failure incidents.
What is the purpose of wire separation in EWIS?
To prevent hazards of interference between wires in a single bundle or between multiple bundles, including mechanical and electrical interference.
What is the failsafe design concept for EWIS?
It assumes that any single failure condition, such as an arc fault, must be considered regardless of its probability.
What are the fire protection requirements for EWIS components?
All EWIS components must meet strict fire and smoke protection requirements to prevent hazardous smoke and toxic fumes.
How should EWIS components be identified?
They must be labelled or identified using a consistent method that facilitates identification of the component, its function, and design limitations.
Fill in the blank: The two most commonly used manuals for electrical installations on aircraft are the Airbus Industries Electrical Standard Practices Manual and the _______.
Boeing D6-54446 Standard Wiring Practices Manual
What are the three types of inspections defined by regulatory authorities for EWIS?
- Stand‐alone General Visual Inspections (GVI)
- Detailed (DET) inspections
- Zonal Inspections
What is a General Visual Inspection (GVI)?
A visual examination of an interior or exterior area, installation, or assembly to detect obvious damage, failure, or irregularity.
What are the key considerations when performing a General Visual Inspection (GVI)?
- Made from within touching distance unless specified
- May require mirrors for visual access
- Conducted under normal lighting conditions
- May require removal of access panels or doors
- Cleaning procedures must minimize anomalies
What types of degradation should a person performing a GVI identify?
- Wear
- Vibration
- Moisture
- Contamination
- Excessive heat
- Ageing
What distinguishes a Detailed Inspection (DET) from a Detailed Visual Inspection (DVI)?
A DET can include tactile assessment, checking components for tightness/security, unlike a DVI which is strictly visual.
What is a zonal inspection?
A collective term for selected General Visual Inspections (GVI) and visual checks applied to each zone, assessing security and general condition.
What are typical EWIS degradation items detectable in a zonal inspection?
- Connectors
- Wire harnesses
- Wire bundle sagging
- Damaged wires
- Corrosion
- Dust and lint accumulation
What factors can compromise connector integrity?
- Worn environmental seals
- Loose connectors
- Missing seal plugs
- Lack of strain relief
What are the areas of concern for wire installations?
- Wire raceway and bundles
- Wings
- Engine, pylon, and nacelle areas
- Accessory compartment and equipment bays
- Auxiliary Power Unit (APU)
- Landing gear and wheel wells
True or False: Paint and/or sealant removal is necessary during a GVI.
False
Fill in the blank: A Detailed Inspection (DET) requires __________ to enhance the inspection process.
direct source of good lighting
What must be checked at grounding points?
- Security
- Condition of the termination
- Cleanliness
- Corrosion
What can lead to wire damage in the cargo bay underfloor?
Maintenance activities in the area and wiring subject to movement or bending.
What is a significant risk associated with terminal lugs and terminal blocks?
Corrosion can cause high resistance and overheating.
What are the consequences of improper clamp installations?
Can aggravate wire chafing and damage insulation.
What is the role of drip loops in wiring installations?
To maintain proper bending radius and prevent tight bends at connectors.
What should be done if signs of overheating are observed in power feeder cables?
Splices or terminations must be replaced.
What is an area where wiring is particularly prone to damage during maintenance activities?
Panel wiring, especially in high-density areas.
What types of contamination can affect wiring in high current areas?
- Coffee
- Food
- Water
- Dust
- Lint
What should be done to clean terminal blocks located in Equipment Power Centres?
Must be kept clean and free of any combustibles.
What is a common cause of wire sagging in bundles?
Adding new wires to existing wire bundles can overload the clamps.
What must be periodically checked to ensure fluid drain plumbing is effective?
Drain path must be free of obstructions.
True or False: The installation of new wiring does not require adherence to approved drawings.
False
What is the impact of excessive flexing at back-shells?
Can lead to wires breaking.
What must be done with EWIS items that show discolouration?
Replace the electrical item.
What is the procedure for repairing cracks in EWIS?
Replace the electrical item.
What is the Enhanced Zonal Analysis Procedure (EZAP) designed to do?
Permit appropriate attention to be given to electrical wiring installations.
What does the EZAP address regarding wiring installations?
Wiring installation discrepancies that cannot otherwise be reliably detected by inspections.
What needs to be assessed to determine inspection levels in EZAP?
Zone size, density of installed equipment, potential effects of fire.
What are the characteristics of zone size in EZAP?
Identified as small, medium, or large.
Define the inspection interval selection in EZAP.
Based on possibility of accidental damage and environmental factors.
What inspection tasks are available for ZIP programmes?
- Zonal GVI
- Stand-alone GVI
- Detailed Inspection (DET)
What are the principal causes of wiring degradation?
- Vibration
- Moisture
- Maintenance
- Metal shavings
- Repairs
- Indirect damage
- Contamination
- Heat
- Ageing
How does high vibration affect wiring?
Accelerates degradation over time, causing ‘chattering’ contacts.
What is the effect of moisture on wiring?
Accelerates corrosion of terminals, pins, sockets, and conductors.
What must be done to prevent metal shavings from damaging wire bundles?
Clean work areas thoroughly during and after work.
What type of splice is recommended for repairing wires?
Environmental splice.
What is wire contamination?
Presence of foreign material likely to cause degradation or sustain combustion.
What special consideration is needed for hydraulic fluid contamination?
Can damage connector grommets and wire bundle clamps.
What are the signs of heat exposure on wiring?
Burned, charred, or melted insulation.
What does ageing refer to in the context of wiring?
Health of the wire’s insulation related to environmental exposure.
Fill in the blank: Wiring that is exposed to high heat can accelerate degradation by causing insulation _______.
dryness.
True or False: A General Visual Inspection (GVI) is always adequate for wiring inspections.
False.
What must be done when waste system spills are found in aircraft EWIS?
Thoroughly clean, inspect, repair, or replace affected components.
What is the primary hazard when servicing waste/water systems near EWIS components?
Electrocution and short-circuit of electrical components
Water is a conductor and can lead to electrocution if it contacts live wires.
What should be done to prevent contamination of EWIS components during repairs?
Cover exposed electronic components and wiring
It is essential to switch off unnecessary electronic equipment in proximity to water.
What maintenance practice can enhance the operational reliability of lavatory systems?
Periodically flush with a weak acid solution
The system must be confirmed to be free of leaks before using acid solutions.
What hazard is associated with servicing oil and hydraulic systems near EWIS components?
Fire hazard
Oil and fluids can emit flammable fumes that can be ignited by live wires.
What precaution should be taken when entering or working on the aircraft?
Prevent damage to adjacent or hidden electrical components
Use protective boards or platforms for adequate support.
True or False: Looms can be used as handholds when working on aircraft.
False
Looms should not be used as handholds, steps, or supports.
What must be ensured when displacing or removing wiring for access?
It must be adequately released from its clamping provisions
Wiring must be returned after the work is completed to avoid damage.
What care should be taken when applying Corrosion Preventative Compounds (CPC)?
Prevent CPC from entering the wire and components
CPC application must follow the aircraft manufacturer’s recommendations.
What is the risk associated with EWIS components in areas with flammable fluids?
Potential ignition source
EWIS components must meet specified requirements to minimize ignition risks.
What are the two types of contamination to EWIS components?
Natural and Accidental
Natural contamination includes materials like hydraulic fluid and dust, while accidental contamination comes from unknown external sources.
What is a mandatory task before working with materials that could contaminate EWIS?
Read the safety data sheets from the manufacturer or supplier
This helps in understanding recommended precautions.
List three safety practices to follow when handling contaminating materials.
- Put on protective clothing
- Ensure proper ventilation
- Do not smoke
Additional precautions include not breathing gas or getting solvents in your mouth.
What should you do if your skin or eyes become irritated while working?
Seek medical help
This is crucial for safety when using potentially hazardous materials.
What is the recommended cleaning material for natural contamination by hydraulic fluid?
Isopropyl Alcohol (Material No. 11-010) or equivalent
Local regulations must also be referred to for compliance.
What should be done in case of accidental contamination?
Treat on a case-by-case basis
Do not use solvents if the contaminating material is unknown.
What is the first step to follow when cleaning EWIS components?
Stop the contamination source
This is essential to prevent further contamination.
What precautions should be taken when cleaning liquid contamination?
- Make a sealed barrier
- Remove contamination with a cloth or vacuum cleaner
This helps control the spread of contamination.
How should powder, granular, or dust contamination be removed?
Remove with a vacuum cleaner
Ensure there are no draughts during this process.
What should be evaluated if the contamination is accidental?
- Characteristics of the contamination agent
- Risk of deterioration of electrical items
- Need for cleaning or replacement
This evaluation helps determine the appropriate response to the contamination.
What is the permitted pH level for cleaning materials used on electrical items?
pH ≤ 11
Cleaning materials with a pH greater than 11 are not allowed.
What cleaning method should be followed?
Start from top to bottom and from the outside to the centre
This methodical approach helps contain the contamination.
What should be ensured about cleaning cloths used in the process?
They should be clean, dry, and lint-free
This prevents additional contamination during cleaning.
True or False: It is acceptable to use any cleaning agent without testing it first.
False
Always test cleaning agents on a small, low-risk area first.
